This new study is an interesting approach to the problem of staging a human asteroid mission. It is written partly in response to the recent NASA Human Exploration Framework Team (HEFT) study, which designed and estimated costs for an asteroid mission in 2026 (the date called for in the Administration’s re-design of our strategic direction in space). The HEFT architecture was briefly famous two months ago, when it was pointed out that it had incorrectly concluded that NASA is unable to build a heavy lift launch vehicle under the Congressionally mandated cost and budget envelope of its recent authorization.

The new GT/NIA study proposes that commercial launch services, coupled with Earth orbital propellant depots, can create the infrastructure needed to stage a human mission to a NEO in 20 years (by 2031). While reviewing details of the study, I was specifically drawn to their cost estimates; the GT/NIA study concludes (depending on the specific launch options selected) that a human asteroid mission can be accomplished (by the time specified for a total program cost) for between $73B and $97B (constant FY2010 dollars). This number contrasts with the HEFT study estimate of $143B (an approach that develops and uses a 100 mT heavy lift launch vehicle).

What benefit do we gain with this expenditure? By 2031, we will have conducted a human mission to an asteroid, thereby reaching the first rung of the Augustine challenge for America’s space program to conduct a “series of space ‘firsts’.” We’ll have emplaced a fuel depot system that can support future human missions to other asteroids, or the moons of Mars (also called for in Augustine’s 2009 “Flexible Path” approach). As NASA will have no launch capability in the future, fuel supplied to these space-based depots will be dependent on commercial deliveries of propellant from Earth. This will be the “new way” of space – depots with fuel supplied by commercial vendors for sortie missions to various and as yet unspecified destinations. All of these missions will be dependent on the necessity of everything needed for space operations being launched (currently, deemed prohibitively expensive) from the surface of the Earth.

I have argued elsewhere that the “launch everything from Earth” template we’ve been locked into for the last 50 years has imprisoned us. Because of the “tyranny of the rocket equation,” we’ve been capability limited – hobbled by upfront launch requirements that consume otherwise useful reserves of mass and power – just to get into space. Propellant depots do not address this fundamental conundrum; they simply obviate the need for a very big launch vehicle by allowing us to stage complex, heavy missions from Earth in smaller increments. Propellant depots are a necessary but insufficient element in a long-term space faring strategy. To truly change the rules of spaceflight, we need to learn how to access and use what we find in space to create new capabilities in space. This involves learning how to use extraterrestrial resources of material and energy.

The Moon was picked as the first destination of the original Vision for Space Exploration because it contains resources in an accessible and readily usable form. By skipping past the Moon, it is certain thatwe will not use space resources for decades because, in order to access and begin using asteroid materials, we will need long-term, if not permanent, presence in the vicinity of the asteroid to characterize, experiment, and learn how to process its resources into usable forms. Initially, robotic missions can begin the characterization of resources, but robots are not sophisticated enough to set up and begin operating a production pipeline, which requires both repetitive and intelligent interaction with the processing. Unlike the Moon, the duration of human presence around a given NEO will be extremely limited by the ironclad laws of celestial mechanics.

It’s interesting to compare the new GT/NIA plan with the lunar return architecture that Tony Lavoie and I recently published. Our architecture also uses propellant depots, initially supplied from Earth but ultimately supplied from the Moon. It creates an expandable, fully functional resource outpost on the Moon, complete, with a reusable, extensible Earth-Moon transportation system capable of exporting rocket propellant to cislunar space within 16 years, at a program cost of $87B.

The affordable lunar return architecture begins the dissolution of space logistics from Earth’s apron strings, leaving in place a legacy infrastructure that can eventually take us beyond cislunar space. Such a system has important scientific, economic and national security value. In contrast, as much as I applaud the GT/NIA effort, their plan spends between $73-97B over 20 years for a single human mission to an as-yet unselected destination, and in the end, has us still launching everything from the Earth.

As painful as this upheaval in the space community has been, it need not be in vain. Both economic and scalable function is required for space operations. A healthy, viable national space program needs purpose and a return on investment. By returning to the Moon and using its resources, we get what we need in order to get what we want.

The LROC NAC observes boulders and blocks located in and around many geologic features on the lunar landscape. How did the boulders get there? Some blocks are observed in ejecta blankets (and the crater itself!) and others are eroding out of sinuous rille walls and the central peaks of craters. Yet others, like the LROC NAC close-up above, highlights boulders that are eroding out of a wrinkle ridge crest.

Today's Featured Image is located to the east of a previous post that examined the presence of several boulder clusters at the crest of a wrinkle ridge in Oceanus Procellarum (see LROC WAC mosaic below for context).

Unlike the wrinkle ridge to the west, today's wrinkle ridge crest is nearly covered in clusters of boulders ranging from about 1 - 6 m in diameter. However, while most of these blocks originate from the ridge itself and are erosive products, there is an ~115 m diameter crater superposed on the wrinkle ridge with boulders scattered along the illuminated wall. Could some of the boulders on the wrinkle ridge be a result of this impact event? Certainly! To test this hypothesis, look for small indentations where the ejected boulder hit the surface. However, if you look carefully at the opening image, there are no boulders on the western rim of the crater, and, of course, the shadow along the western crater wall makes it very difficult to tell if there are boulders there.

It is possible that the boulders on the illuminated portion of the crater wall are a result of post-impact modification and erosion within the crater itself and that these boulders are not from the top of the ridge - there are no visible boulder trails. Based on these observations, the boulders probably are eroded (and eroding!) fragments of ridge material fractured during deformation, and while LROC scientists do not have a definite answer at this time, they are analyzing hundreds of LROC NAC images with bouldery wrinkle ridges to try to solve this question!

Take a look at the length of the wrinkle ridge in the full LROC NAC frame - is there any evidence that some boulders do not originate from the ridge crest?

Typical highland lunar landscapes are heavily cratered, and the craters that mark the surface provide a record of the impact history for that area. Today's Featured Image highlights the effects of discontinuous ejecta (which forms secondary craters) on the lunar surface. When material is excavated during impact, much of that material is deposited very close to the crater - generally within 1 crater diameter. This material is called the continuous ejecta blanket. However, most impacts are so energetic that ejecta is deposited not only near the crater but also much, much farther away. This far-reaching ejecta is part of the discontinuous ejecta blanket and is responsible for forming secondary crater chains, clusters, and rays. The erosive energy of the secondaries is quite large - in the opening image, ejecta scoured the wall and rim of the crater, leaving behind deep grooves!

This region of farside highland terrain is east of Orientale, and an asterisk notes the location of the LROC NAC image above in this LROC Wide Angle Camera (WAC) monochrome mosaic, [NASA/GSFC/Arizona State University].

Looking at the full LROC NAC frame, secondary crater chains follow the grooves toward the northeast. Because secondary crater chains and streams represent the direction from which the ejecta came, scientists can use these features to try to determine which impact was responsible for them. The secondary crater chains trend southwest to northeast, determined by observing the direction of the majority of these features in this NAC frame. Furthermore, these secondaries probably originated from the southwest because many of the craters within the chains are tear-drop shaped. Looking around the region in the LROC WAC mosaic presents many possibilities for the source impact. Although not pictured in the WAC mosaic above, we probably can rule out Orientale basin as the source for these secondaries because the ejecta should be trending west to east and it is not. However, Byrgius A is a Copernican-aged crater (it still has visible rays) and lies to the southwest of the area in today's Featured Image; perhaps Byrgius A is the source of the secondaries scouring the landscape in the NAC frame.

Tuesday, March 22, 2011

Detailed View of the Solar Corona, "a stream of energetic particles flowing from the Sun, the solar wind," and the Moon holds the best unvarnished record of the Sun's activity as collected near Earth over 4.5 billion years. Astronomy Picture of the Day, March 16, 2010; a detailed image of the Sun's corona during the August 2008 total eclipse from Mongolia. No history of Earth can be complete without a thorough study of the Moon, the "Rosetta Stone of the Solar System." View the full-sized original image HERE [Miloslav Druckmüller (Brno University of Technology), Martin Dietzel, Peter Aniol, Vojtech Rušin].

But in fact, we do have an excellent historical record of the Sun’s history – preserved on our nearby Moon.

The Sun constantly emits streams of high-energy particles, consisting mostly of hydrogen atoms and ions (protons). This stream, called the solar wind, has been monitored and studied since satellites were first launched. High-energy solar wind flows around the protective bubble of Earth’s global magnetic field and into interplanetary space. Some of these charged particles become trapped between magnetic lines of force, creating spectacular displays of aurora, known as the “northern lights.”

The Moon does not have a global magnetic field, so its surface is directly exposed to the solar wind. These charged particles and neutral atoms impinge directly upon the surface, where some of its atoms are retained on the grains, thus creating a recoverable record of matter from the Sun. The antiquity of the lunar surface means a preserved solar record extending back at least several billion years – the average age of the surface units of the Moon.

We have measured solar wind gas implanted onto the dust grains of the Moon using the Apollo samples and have a good indication that this record contains some significant information. One curious and obscure relation in the solar wind record recovered from the Moon suggests that the ratio of some isotopes of nitrogen (specifically, the 15N/14N ratio) has increased over the last couple of billion years. This increase is not predicted in current models of stellar evolution; the current interpretation is that it reflects the addition of a meteoritic component, but changes in the solar output have not been ruled out. So the Sun may be evolving and changing in ways we do not fully understand.

The Sun literally is responsible for our existence – without it, life on Earth would not be possible. Media coverage of climate change tends to ignore the critical fact that the primary driver of climate on Earth and all terrestrial planets is the Sun. Before we can understand how and why climate changes on Earth (and it has repeatedly throughout geological history), we must understand what historic role the Sun has played in this complex exchange.

At any given time, only the uppermost few millimeters of the Moon’s regolith is exposed to the Sun. Because the regolith is continually excavated, buried, mixed and turned over by the bombardment of meteorites, we have a very complex record to decipher. Such a chaotic, random process would seem poised to destroy exactly the very information we need to access and study, similar to the destruction of scientific clues about past climatic conditions on our geologically dynamic Earth. But our nearest neighbor has provided a process that preserves the solar record in ancient regoliths, whereby the solar record is isolated and sequestered for very long periods of time.

The dark maria of the Moon is made up of a myriad of individual lava flows, erupted sporadically but continuously, since 3.9 billion years ago, possibly to as recently as less than 1 billion years ago. These fresh surfaces are readily exposed to the solar wind, which implants its atoms onto the dust grains. From the moment the lava flow cools, this fresh surface is slowly ground up and broken apart by meteorite impact (regolith formation). Then, as new lava flows are extruded, they cover the pre-existing surface regolith, forever sealing it off, along with its preserved solar record, from active surface processes. Thus, thousands of individual lava flows in the maria have buried and preserved millions of ancient regolith deposits, all potentially available for study, allowing us to see not only the output of the current Sun, but the solar wind record of some ancient Sun as well.

Here is yet another reason to return to the Moon: to understand the history of our Sun, the primary driver of climate and life on Earth. It is ironic that many people who are most ardent in their concern about Earth’s changing climate disparage lunar return because “we’ve been there.” By dismissing the Moon, they are missing one of the most important chapters necessary in understanding the grand story of the past, present and probable future of the Earth and the Solar System. That chapter – holding vital answers necessary for an informed debate about our constantly changing climate – patiently waits for us on the Moon.

The second Full Moon of December 2009 grazed the Earth's shadow; a New Year's Eve "Blue Moon" partial eclipse captured in this two exposure composite in cloudy skies over Saint Bonnet de Mure, France. Playing across the Moon's southern reaches, the edge of Earth's umbra, our dark central shadow, appears on the right side along with the prominent 109 million year old "young" ray crater Tycho. At Maximum the umbra covered only about 8 percent of the lunar disk.

This unnamed 740 meter-in-diameter crater has bouldery walls and is morphologically similar to many 1 kilometer or less in diameter craters in the lunar mare. Image field of view is 847 meters, LROC Narrow Angle Camera observation M127328861L, LRO orbit 3898, October 10, 2010 [NASA/GSFC/Arizona State University].

Lillian OstrachLROC News System

The LROC NAC has imaged thousands of blocky craters similar to this example found in Oceanus Procellarum. The numerous boulders may be fragments of bedrock, regolith breccias formed by the impact itself, or a combination of both. Since a crater depth of excavation is roughly one tenth its diameter, this small crater has probably distributed material from about 75 meters depth around its rim. Usually, ejecta material on the rim comes from the deepest part of the crater, and ejecta farther away from the crater comes from shallower depths. Thus astronauts can walk towards a crater rim, sampling material from greater depths as the rim is approached in a radial cross-section of the ejecta blanket. As you look at these boulders, you are witnessing a history of the emplacement of this mare. If we could just pick up samples and bring them back to Earth, we could figure out how much time elapsed between mare basalt flows in this area and how much the composition changed with time.

The vast Oceanus Procellarum mare basalts are observed in this portion of LROC Wide Angle Camera monochrome M117895651M. Prominent across the scene are wrinkle ridges and secondary crater clusters. The arrow points to the blocky crater in the opening image. See the full-sized image release HERE [NASA/GSFC/Arizona State University].

Come home with your shield, or on it – Spartan women to their husbands, marching off to war.

From the giant Olympus Mons shield on Mars (600 kilometers across and 27 km high) to the large volcanoes of Venus, shield-building was thought to be a common expression of volcanism on all rocky Solar System bodies; the Moon appeared to be a conspicuous exception. In geology, a shield volcano is a volcanic construct with a broad, low profile made up primarily of thin lava flows with little ash deposits. Earth’s shield volcanoes range in size from a few to more than 200 km for the Big Island of Hawaii, the extent of its base on the sea floor beneath the surface of the Pacific Ocean.

Our understanding of lunar volcanism has been informed and shaped both by images and samples. The large-scale shield volcanoes so prominent on Mars, Venus and Earth were believed to be absent on the Moon. Before the Apollo 11 astronauts visited Mare Tranquillitatis in 1969, we understood that the dark maria of the Moon were volcanic lava plains. Orbital images showed us a landscape of domes, small cones, sinuous lava channels (rilles) and collapse pits – surface features created by volcanic activity. Many of these small volcanic features tend to be clustered in provinces concentrated on the western near side.

Rocks from the maria are basalts, the most common type of igneous rock in the Solar System. They are rich in iron and magnesium and poor in silica. On Earth, when such rocks are molten, the resulting magma has a very low viscosity (i.e., they are very fluid, spreading onto flat surfaces in thin sheets). We understand lunar lavas to be similarly fluid, having erupted in thin sheet-like flows onto the airless surface of the Moon. The maria formed as this geologic process of massive high-volume eruptions built up stacks from the thin, fluid flows which extend for hundreds of kilometers. Scattered within the ancient maria are numerous small volcanic constructs, previously believed to be the only manifestation of central-vent volcanism on the Moon.

When the Moon’s topography was mapped with laser altimetry (first by Clementine in 1994, then at greater resolution by the Japanese Kaguya spacecraft and NASA’s Lunar Reconnaissance Orbiter mission), it showed clusters of many small volcanoes occurring on topographic highs that are quasi-circular, with low relief and shield-shaped. Pat McGovern, Walter Kiefer (colleagues at the Lunar and Planetary Institute) and I were intrigued by this correspondence. We studied these areas by mapping volcanic features, integrating the new topographic data, and examining their gravity signatures (the amount the local gravitational attraction is enhanced or depleted from normal).

We found that these large shield-shaped topographic swells are made of basaltic lava and display concentrations of volcanic features. Such a structure found on Venus or Mars would be classified as a shield volcano; therefore, we interpret these features on the Moon as shield volcanoes. We have found seven of these large structures on the Moon, ranging in size from 66 to almost 400 kilometers in diameter and from 600 to over 3200 meters in height. Such sizes and shapes are very similar to large shields on Earth, Venus and Mars. The average slopes on these volcanoes are very low, typically less than a few degrees, as would be expected for structures made from very fluid lava. These lunar shields display abundant volcanic features, including domes and cones, sinuous rilles (lava channels and tubes) and collapse features – all common morphologies in terrestrial shield volcanoes.

Topographic map of the Marius Hills shield on the Moon from LOLA laser altimetry. A broad topographic swell with many small cones and domes on it [NASA/GSFC].

Although we believe these features are shield volcanoes, this new interpretation is not without some difficulties. Unlike most shield volcanoes on the other planets, none of the lunar shields has a central collapse pit (caldera). However, many shields – especially those on Venus – likewise do not show central calderas. Additionally, while evidence for some lunar shields such as the Marius Hills is pretty convincing (e.g., shield shape, high gravity signature indicating dense stacks of lava), the evidence for others is not as clear. The largest feature we identified, the Cauchy shield, possesses the correct topographic shape and has numerous small cones, rilles, and vents on it, but remote sensing data suggest that the lava thickness in eastern Mare Tranquillitatis is relatively thin, which might mean that Cauchy is not a thick stack of lava as Marius appears to be. We still think that Cauchy is a shield volcano, but acknowledge that our interpretation is tentative and we will continue studying these enigmatic features to better understand their history.

But the real story here is not whether these features are true shield volcanoes or not, but rather, how the advent of new, high-precision data (high resolution topography) can cause scientists to reexamine areas and processes long thought understood and perhaps come to surprisingly different interpretations. We are currently in the midst of a revolution in lunar science. The 42nd Lunar and Planetary Science Conference held this month in Houston highlighted new scientific findings about the history and processes of the Moon. New, high-quality data coming from an international flotilla of lunar orbital mappers – Chandrayaan, Kaguya, Chang’E and LRO – has scientists seriously reconsidering our current understanding of the processes, history, resources and potential of the Moon.

Saturday, March 19, 2011

The beginnings of public access to the developing "Quickmap" service, linking LROC Narrow and Wide Angle Camera photography is astounding and immediately useful. It was possible to identify excellent candidates for artifacts not yet publicized, like the impact crater of the Apollo 17 lunar module ascent stage "Challenger" and possibly Luna 9, for example [NASA/GSFC/Arizona State University].

Its a lot of fun! Start at reduced WAC resolution and end up on the surface at full NAC resolution. Quickmap is brand new (and not 100% refined). But, it's ready for testing!

Give it a try and watch it improve over the next several months.

We hope you like it!

It was immediately possible to focus in on regular NAC observations of Tranquility Base and the rich context of its vicinity in southwestern Mare Tranquillitatis, picking the high glint off the Apollo 11 lunar module descent stage at a resolution of only 64 meters per pixel [NASA/GSFC/Arizona State University].

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft became the first spacecraft ever to enter Mercury's orbit! The insertion burn occurred 18 March 2011 at 12:45 am UTC (17 March, 8:45 EDT). The MESSENGER spacecraft traveled about 4.9 billion miles to reach the point for orbital insertion. Read more about the successful MESSENGER orbital insertion!

Today's Featured Image is the Moon as seen from the MESSENGER spacecraft on July 31, 2005, less than a year after the spacecraft's launch from Cape Canaveral. The lunar image was taken by the MESSENGER Wide Angle Camera (WAC), which is part of the Mercury Dual Imaging System (MDIS). At the time when the image was taken, the spacecraft was about 992,814 kilometers (616,906 miles) from the Earth.

This image was not taken simply because the Moon is beautiful and inspiring; it serves to help the MESSENGER team calibrate the camera and spectrometer. The Moon is a good calibration standard because its reflectance and color have been measured with many instruments, so it is useful to make comparisons between instruments with different characteristics. In other words, it is a check on the quality of the Earth-based calibration.

LROC is an important new contributor to our understanding of how light interacts with the lunar surface especially in ultraviolet wavelengths. In particular, the new WAC color images will help to calibrate the MESSENGER MASCS spectrometer, which measured the Moon at the same time the MDIS camera snapped this picture.

The MESSENGER MDIS view of the Moon is centered about -60°, 280°. Mare Orientale is the the small dark spot in the upper left. For a closeup of Orientale see the recent LROC Featured Image. The same viewpoint as the MESSENGER image was used to create a higher resolution view from the LROC WAC.

After the orbital insertion, scientists will test the spacecraft systems to make sure that all the instruments are in good working order. It is important to verify that all the instruments operate well in the harsh thermal environment around Mercury (currently Mercury is only about 0.3 AU from the Sun!). On April 4, 2011, the science phase of the MESSENGER mission will begin and the orbital science data from Mercury will be returned to Earth almost every day for at least a year! For more news about the MESSENGER mission, visit the NASA news page.

Congratulations to the awesome MESSENGER spacecraft operations team at APL!

Thursday, March 17, 2011

At 109 km in diameter, north polar farside crater Plaskett (81.8°N, 176.5°E) displays the morphology of a typical complex crater. For example, both a central peak and terraced crater walls can be seen in Plaskett. Its central peak formed during the impact process when material at depth below the crater floor rebounded due to the excavation of the crust and resulting release in pressure.

Central peaks are interesting to scientists because they provide a glimpse of what lies deep below the lunar surface. LOLA data can be used to study the morphology and depth of craters like Plaskett in unprecedented detail, and in so doing, increase our understanding of the impact process.

Japan's lunar orbiter SELENE-1 ("Kaguya") returned famous HDTV orbital earthset and earthrise sessions in November 2008. Coming up over the Moon's north polar latitudes, Kaguya captured this spectacular natural color view of Earth rising into view over Plaskett, along with the long shadows of the crater's central peak region, even at just after mid-day in the Moon's far north [JAXA/NHK].

One of the primary scientific objectives of the Lunar Reconnaissance Orbiter Camera (LROC) is to identify regions of permanent shadow and near-permanent illumination. Since the start of the nominal mission, LROC has acquired thousands of Wide Angle Camera (WAC) images approaching the north pole. From these images we produced two very different types of mosaics. The more conventional mosaic is shown above and is composed of 983 images taken over a one month period during northern summer. This mosaic shows the pole when it is best illuminated, regions that are in shadow are candidates for permanent shadow. The best way to determine lighting conditions with image data is to take many pictures over a year and stack them up. From orbit-to-orbit, the WAC frames overlap from about 88Â°N to the pole. At each point you count how often that pixel is illuminated and create a percentage illumination map. You can also think of this mosaic as a multi-temporal mosaic.

WAC illumination map, brighter tones represent areas with more illumination during a year, the area shown is from 88°N to 90°N. Full-size release HERE [NASA/GSFC/Arizona State University].

A more dramatic way of displaying this multi-temporal dataset is the movie (600 m/p). below, posted on YouTube. Download the full-resolution Movie, HERE. Watch closely - can you spot any regions that are nearly always illuminated?

Tuesday, March 15, 2011

LROC Wide Angle Camera (WAC) mosaic centered on Orientale basin. From the center of the mosaic to a corner is about 2000 km. View the full LROC 1600 x 1600 Featured Image HERE [NASA/GSFC/Arizona State University].

The 5th LROC Planetary Data System (PDS) release includes images acquired between September 16, 2010 and December 15, 2010, during the Science mission phase. This release includes 69,505 Experiment Data Record (EDR) images totaling 8,498 Gbytes and 69,528 Calibrated Data Record (CDR) images totaling 17,651 Gbytes worth of data.

The LROC Team is also making it's first Reduced Data Record (RDR) release this week, which represents a culmination of many months of work calibrating, map projecting, and creating mosaics and topographic maps from NAC and WAC images. The RDR release includes a global WAC monochrome mosaic, NAC mosaics for 40 regions of interest (ROI), numerous NAC DTM products, NAC North and South Polar mosaics, several example WAC UV and VIS regional mosaics, and over 8,000 WAC North and South Pole observations used to create movies of each poles lighting conditions over time. The RDR release totals over 8,400 images totaling over 2 Tbytes of data.

At full-resolution, zooming in on the Orientale pyroclastic vent perched at the center of a dark "smoke ring," of darker material draped upon the mountainous southwestern edge of the Orientale basin. The vent interior has already been imaged in great detail by the LROC Narrow Angle Camera, but the WAC mosaics deliver unprecedented context and depth of field [NASA/GSFC/Arizona State University].

Today's Featured Image is an orthographic re-projection of the WAC global mosaic centered on the youngest large basin on the Moon, Orientale. This basin is barely visible on the western limb of the Moon as seen from the Earth. Its existence was not confirmed until spacecraft sent back images of the farside 50 years ago. Unlike other large basins, Orientale has very little volcanic materials filling its interior, so the basin structure is easily seen. The inner and outer basin rings are particularly obvious - imagine if the Moon were rotated 90° and the Orientale basin faced the Earth. What sort of mythology would have grown up around the great eyeball in the sky?

Backing away, the vent is harder to discern, though the ring of darker material surrounding it makes the feature easier to pick out. Compare this with the high-sun incidence view further below taken from Galileo on its way toward Jupiter in 1990 [NASA/GSFC/Arizona State University].

The new WAC Orientale mosaic also reveals striking detail in the far-flung ejecta blanket. Note the radial chains of secondary craters formed as large chunks of the Moon were thrown hundreds of kilometers! These same type of large impacts occurred on the Earth also - fortunately the era of heavy bombardment ended about 3.9 billion years ago!

Early in the Galileo mission to Jupiter, the probe used Earth's Moon to test and baseline it's remote sensing capabilities. During a second gravity-assist fly-by of the Earth-Moon system in 1990, JPL turned the probe's cameras on the Moon's western hemisphere and swept up this late morning overhead view of Mare Orientale [NASA/JPL].

Linné (27.7°N, 11.8°E) is a very young and beautifully preserved impact crater. LROC stereo images provide scientists with the third dimension - information critical for unraveling the physics involved in impact events. The LROC science team presented a first analysis of Linné crater topology at the Lunar and Planetary Science Conference last week.

The high resolution topographic model also provides the means to make synthetic views of the crater from any angle. By creating hundreds of such views and slightly changing the view point for each image a dramatic fly around movie appears on the screen.

Today the LROC team released a set of NAC stereo derived map products. LROC NAC Digital Terrain Models (DTM) are made from geometric stereo pairs (two images of the same area on the ground, taken from different view angles under nearly the same illumination). LROC was not designed as a stereo system, but can obtain stereo pairs through images acquired from two orbits (with at least one off-nadir slew). Off-nadir rolls interfere with the data collection of the other instruments, so LROC slew opportunities are limited to four per day.

Reduced resolution (2 meter pixel scale) mosaic of Linné, context for the location of the higher resolution images accompanying LROC Featured Image "Landmark Linné of Serenitatis," July 7, 2010. Linné (27.7°N, 11.8°E)is a landmark crater for amateur observers minimally equipped with 200mm reflecting telescopes. As with most such observations, Linné is most easily spotted when highlighted by the lengthy shadows of local sunrise or sunset, six days after a New Moon or five nights after Full [NASA/GSFC/Arizona State University].

To a generate a DTM, we use a combination of the USGS Integrated Software for Imagers and Spectrometers (ISIS) and SOCET SET from BAE Systems. ISIS routines ingest the image files, perform a radiometric correction, and export to a format SOCET SET accepts. Next an analyst runs through several procedures, including detailed quality control, that take about a week to complete a DTM.

Once a DTM is complete we make derived products: orthorectified image, shaded-relief image, color shaded relief image, color slope map, and a confidence map. An orthorectified image has all topographical and camera distortions removed. These images are cartographically true and can be used to measure accurate distances. A shaded-relief generated using the DTM simulates the Moon's surface with a light source casting shadows on the terrain. Color coded elevations are draped on the shaded relief to form the color shaded relief map. Finally, slopes derived from the DTM are color coded to help users better discriminate subtle changes in elevation. A confidence map indicates the quality of the elevation estimate at each pixel. The standard PDS products include the DTM and orthorectified images in two resolutions (resolution of the DTM and resolution of the original images), and the confidence map. Also the shaded-relief, color shaded-relief, color slope map, and DTM are provided in GeoTIFF format.

For more information on the methodology and preliminary error analysis of the DTMs, see Tran et al. 2010.

Apollo 17 commander Gene Cernan, back in the Lunar Module Challenger, is photographed by LM pilot Harrison Schmitt completing a total 22 hours, 6 minutes, 45 seconds on the lunar surface at the end of EVA-3, December 14, 1972 [NASA/ALSJ].

"We had to take some chewing gum, Dentyne chewing gum, on Gemini IX, just to keep our mouth refreshed," Gene Cernan said in a 2007 NASA oral history. "We couldn't take toothpaste and toothbrushes, because what are you going to do with the toothpaste? Well, we're going to swallow it. Oh, you can't swallow it."

Cernan, born on March 14, 1934, made three spaceflights, his final one as Apollo 17 commander. Before climbing into the lunar module Challenger, he left man's last footprints on the Moon.

"We leave as we came and, God willing, we shall return with peace and hope for all mankind," The Associated Press reported Cernan said.

"I never even thought about (my words) until I was crawling up, basically crawling up the ladder," Cernan said in the Dec. 11, 2007 oral history, on the 35th anniversary of his lunar landing.

Cernan was at Purdue University when he "received his commission through the Navy ROTC Program," the website jsc.nasa.gov said. In October 1963 NASA chose him among 14 astronauts. In 1966 he piloted Gemini IX, becoming "the second American to walk in space"; he was outside the capsule for two hours and 10 minutes. Subsequently, he was "backup pilot for Gemini 12 and ... backup lunar module pilot for Apollo 7," and later " backup spacecraft commander for Apollo 14."

Cernan's second flight was in May 1969, as Apollo 10 LM pilot. He descended "to within (eight) nautical miles of the lunar surface," jsc.nasa.gov said, "demonstrating that man could navigate safely and accurately in the moon's gravitational fields."

Taurus-Littrow Valley, skirting the eastern shore of Mare Serenitatis, the landing site of Apollo 17 as seen from the general but simulated perspective along a line-of-sight view from Earth. The pitch-over before landing took place over the mountainous terrain on the Valley's eastern side. LROC Wide Angle Camera monochrome mosaic centered at 0 degrees longitude (the lunar nearside) [NASA/GSFC/Arizona State University].

Apollo 17 launched on December 7, 1972, "the first manned nighttime launch," said jsc.nasa.gov. Four days later, Cernan and Harrison Schmitt touched down at Taurus-Littrow.

He "waited a long time for December 11, 1972 to come around," Cernan said. "I'm flying. A lot of people think we pressed a button and let the thing fly itself. There's no way I'm going to go all the way to the Moon and let a computer land me on the Moon. The arrogance of a pilot, particularly naval aviators, is too great to allow that to happen. Nobody ever landed on the Moon other than with their own two hands and brain and eyeballs."

Saturday, March 12, 2011

The lunar farside as never seen before. LROC Wide Angle Camera orthographic projection, centered at 0°N, 180°E. The Lunar Reconnaissance Orbiter Camera (LROC) team has now released a complete compliment of 100 meter resolution, contiguous illumination mosaics from a perspective over the Moon's equator. The full-sized (1600 x 1600) image is available HERE [NASA/GSFC/Arizona State University].

And what a surprise -­ unlike the widespread maria on the nearside, basaltic volcanism was restricted to a relatively few, smaller regions on the farside, and the battered highlands crust dominated.

A different world from what we see from Earth.

Of course, the cause of the farside/nearside asymmetry is an interesting scientific question. Past studies have shown that the crust on the farside is thicker, likely making it more difficult for magmas to erupt on the surface, limiting the amount of farside mare basalts. Why is the farside crust thicker? That is still up for debate, and in fact several presentations at this week's Lunar and Planetary Science Conference attempt to answer this question.

The Clementine (1994) mission obtained beautiful mosaics with the sun high in the sky (low phase angles), but did not have the opportunity to observe the farside at sun angles favorable for seeing surface topography. This WAC mosaic provides the most complete look at the morphology of the farside to date, and will provide a valuable resource for the scientific community. And it's simply a spectacular sight!

One of the primary objectives of LROC is to provide a global 100 m/pixel monochrome (643 nm) base map with incidence angles between 55°-70° at the equator, lighting that is favorable for morphological interpretations. Each month, the WAC provides nearly complete coverage of the Moon under unique lighting. As an added bonus, the orbit-to-orbit image overlap provides stereo coverage.

Reducing all these stereo images into a global topographic map is a big job, and is being led by LROC Team Members from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). Several preliminary WAC topographic products have appeared in LROC featured images over the past year (Orientale basin, Sinus Iridum).

For a sneak preview of the WAC global Digital Elevation Model (DEM) with the WAC global mosaic, view a rotating composite Moon (Full Resolution), HERE. The WAC topographic dataset will be completed and released later this year.

The global mosaic released today is comprised of over 15,000 WAC images acquired between November 2009 and February 2011. The non-polar images were map projected onto the GLD100 shape model (WAC derived 100 m/pixel Digital Terrain Model - DTM), while polar images were map-projected on the LOLA shape model. In addition, the LOLA derived crossover corrected ephemeris, and an improved camera pointing, provide accurate positioning (better than 100 m) of each WAC image.

As part of (their) March 2011 release to the Planetary Data System (PDS), the LROC team posted the global map in ten regional tiles. Eight of the tiles are equirectangular projections that encompass 60° latitude by 90° longitude. In addition, two polar stereographic projections are available for each pole from ±60° to the pole. These reduced data records (RDR) products will be available for download on March 15, 2011.

As the mission progresses, and our knowledge of the lunar photometric function increases, improved and new mosaics will be released! Work your way around the Moon with these six orthographic projections constructed from WAC mosaics. (The nearside view linked below is different from that released February 21.)

Six orthographic views of the Moon created from the new Lunar Reconnaissance Orbiter Camera WAC global mosaic; upper left to lower right the central longitude is 0°, 60°, 120°, 180°, 240°, 300° East longitude. View the full preview image above HERE [NASA/GSFC/ Arizona State University].

Peary Crater (88.6N, 33.0E), diameter 73 kilometers, near the lunar north pole, has been a subject of interest for many lunar and planetary scientists for years. In the 1990's NASA's Clementine mission imaged the crater, and scientists identified regions surrounding Peary that they suspect remain constantly in daylight throughout the 28 day lunar cycle [1]. However parts of Peary's interior remain in permanent shadow at all times, providing only limited views of its contents [2]. Topographical data from LOLA reveal details hidden in permanently shadowed regions, like those in Peary, that visible light cameras cannot image. View the full-sized LOLA Featured Image HERE [NASA/GSFC].

Karrer (52.13°S, 142.31°W) is mare-filled crater on the far side of the Moon, approximately 51 km in diameter. Karrer is special because there are fewer mare basalt surfaces on the far side compared to the near side of the Moon.

Within Karrer crater's mare basalt covered floor is a lobate scarp, unofficially designated as Karrer scarp for the crater within which it is located. Today's image shows a section of this scarp, where the deformation of the mare basalt is close to forming the shape of two right angles. Mare basalt surfaces often have lobate scarps and wrinkle ridges, two types of contractional tectonic features. In the WAC monochrome mosaic (below), you can see that the scarp extends south outside the rim of Karrer crater onto highlands material. Lobate scarps are thought to be the surface expression of thrust faults, formed when an upper fault block is pushed up and over a lower fault block.

LROC Wide Angle Camera (WAC) 100 meter per pixel monochrome mosaic of the mare-filled crater Karrer. The lobate scarp runs approximately north-south through the crater's interior basin. For a full-sized view of this contextual image, click HERE [NASA/GSFC/Arizona State University].

As LRO's Science Mission observation become available, an opportunity presents itself to gather further observations of a target area, courtesy of the LROC team and the Planetary Data System. The WAC view above of Karrer's interior, for example, was swept up at the same time as the Featured Image, November 28, 2010 [NASA/GSFC/Arizona State University].

Stepping back in pixel depth brings Karrer and its immediate vicinity into view, in this monochrome (604nm) mosaic stitched together from six orbital passes, during which time the lunar surface rotated eastward under LRO's 54 km-high orbit, at that time [NASA/GSFC/Arizona State University].

Even at a simulated perspective of 12 kilometers over the mosaic, draped on the lunar digital elevation model available to users of Google Earth (version 5 and higher), the south rim of Karrer is16 km below. Situated on the eastern side of ancient and deep South Pole-Aitken basin, not far from the Apollo basin, Karrer's rim is 4100 meters below mean lunar elevation.